iPod - Keeping all podcasts off of my Nano 3G?

Can anyone tell me why, even though I've got the Sync checkbox unchecked in the Podcasts tab of my Nano 3G in iTunes (Mac OS X), when I plug the Nano in to sync it with my music library, it often starts putting podcasts on the Nano as well (and then complains that there isn't enough room)? The only way I've been able to get those podcasts back off of the iPod when syncing is to also tell iTunes to "only sync checked songs and videos", and then go in and manually uncheck each and every podcast, which is a pain. So what's the story here? Am I doing something wrong?

Good idea on the Recently Played playlist, except that there aren't any podcasts on that. However, there WERE several new podcasts on my Recently Added playlist, and now I suspect that's where the synced podcasts are coming from (as it is always the latest downloaded ones that seem to get pushed onto the Nano).

Is there some way for me to keep all of my music automatically syncing and still remove a playlist from syncing? It looks to me like the only way I can exclude a playlist is by selecting to only have selected playlists synced, and I don't have all of my music in playlists. Maybe if I create an automatic playlist that includes all of my music?

With the help of all of your combined words of wisdom, I think I've figured it out. I did change my settings to only sync with selected playlists. I then added an all-music smart playlist that basically just excludes podcasts and video files, and enabled that one for syncing (along with the other playlists I actually use). Seems to have worked like a charm, and now I've got all of my music plus enough space left over for the next CD or two that I buy (yay!).

Thanks everyone! I'd never even noticed that podcasts were showing up in the "Recently Added" playlist until you guys set me on the right track.